Cons:

Perhaps more than any year that's come before it, 2008 could be called The Year of Living Cooperatively. This holiday season has seen the release of many excellent co-op games on every gaming platform, from Gears of War 2 to Call of Duty: World at War to Resistance 2. While all of those games are great examples of where co-op gaming could be headed in the future, for the last few months our eyes have been focused squarely on Valve's Left 4 Dead. Instead of just shoehorning a second player into a traditional single-player campaign, Left 4 Dead has been specifically built for co-op play from the ground up, and the resulting product is one of the most intense, enjoyable gaming experiences to date. It gets better with every human player that's added, to the point that playing with three of your friends is close to gaming nirvana.

The basic premise of Left 4 Dead puts four characters in the middle of the worst horror-film scenario: surrounded by hordes of "infected" and running for their lives to a rescue point. The actual origin of the infected is never clarified, nor is it that crucial; what matters is that at every turn, there's a chance that a few dozen zombies might come charging at you at full speed, looking to claw you apart. Then there's the threat of a few special "boss" zombies that appear now and then to really make a mess of things. And so you need to team up with three chums to fight through city streets, office buildings, highways, farms and sewers to keep from becoming zombie chow.

If you're looking to do some solo training before playing with friends, you can take on the four different episodes with AI-controlled bots covering your back. Although it's exactly the same game, and just as exciting, it's a very different experience, because the bots are very well-programmed. They play it safe, cover your back, spot boss zombies as soon as they show up... in short, all the things that you'll soon wish your human friends were good at. The "real" fun of Left 4 Dead is screaming at your clueless human buddies as they run off like Rambo, or using teamwork to navigate your way through a particularly sticky situation. This just doesn't happen when playing by yourself, as your AI squadmates will stay near your side almost all of the time, leaving most of the action for you and only helping out when you really need it.

Once you have friends on your side, it's one hell of a ride. With dozens of zombies swarming you at any given moment and the yells of your friends echoing in your ears, the action in Left 4 Dead is as intense as any game in recent memory. This is one of those games in which you'll need to use teamwork and communication if you hope to survive, as things have a tendency to go FUBAR as soon as someone decides to make a go of it on their own. Friendly fire is always on, so you have to watch your aim. The enemy AI is tenacious, and the hordes of the undead will swarm you as soon as you fire a shot, so it's not uncommon for one gung-ho player to wander off, get attacked, and require a rescue from his or her comrades. Rescuing one of your buddies while simultaneously dealing with dozens of zombies is hard enough, but it gets even more challenging once the special infected are thrown into the mix.

The powers of the special infected force you to deal with some unique situations. In the case of the Smokers and Boomers, it's usually relatively easy to kill them before they pull you away with their tongues or vomit zombie-attracting bile on you, respectively, but it's easy for them to sneak up on you while you're dealing with the horde. Far tougher are the Tank and the Witch. The Tank simply requires a ton of ammo to take down. The Witch will leave you alone if you don't bother her, but that's hard to do when bullets are flying in every direction; once awakened, you don't want to be anywhere near her. Thankfully, you'll be able to audibly discern whether a special Infected is nearby, provided you can hear over the cacophony of screams and gunfire.